'07 Honda Odyssey 1st drain & fill

[Vikas]

I can tell you that there is no method that will "swap" the old fluid with the new fluid. That physical impossibility.

Mathematically, it can be proven that doing multiple drain and fill will the "most" of the fluid replaced but it can never be 100% new.

for all practical purposes, if you did it 5 times, over 90% of the fluid will be new.

Do this every weekend for five weeks and you have brand new fluid in the system.

- Vikas

 

[artbuc]

Originally Posted By: Vikas
Do this every weekend for five weeks and you have brand new fluid in the system.- Vikas


Only problem with this approach is the 5-6 qts of ATF you waste.

 

[artbuc]

Originally Posted By: Vikas
I can tell you that there is no method that will "swap" the old fluid with the new fluid. That physical impossibility.- Vikas


True to the extent there is some backmixing in the TC and a portion of the pump discharge goes back through the valve bodies into the sump. However, diverting ATF out of the cooler return line is far more efficient than multiple drain/fills. In my Toyota/Lexus, the transition from old to new ATF happens in less than 1 quart. If you want to go over the top, you can drop the pan, connect a fresh ATF supply to the pump suction and collect ATF from cooler return and valve bodies. Even I wouldn't go that far.

 

[DuckRyder]

Could someone try to explain to me the logic of driving the car for extended periods between the drain and fills.

In my mind this would only serve to more thoroughly mix the old and new fluid.

It seems to me that if you drain and refill the pan, the goal should be to get the new fluid into the transmission and the old fluid into the pan so you can drain it with minimal mixing.

This appears to be what the above linked Honda procedure tries to accomplish.

 

[DuckRyder]

Originally Posted By: artbuc
Originally Posted By: DuckRyder
Could someone try to explain to me the logic of driving the car for extended periods between the drain and fills.

In my mind this would only serve to more thoroughly mix the old and new fluid.

It seems to me that if you drain and refill the pan, the goal should be to get the new fluid into the transmission and the old fluid into the pan so you can drain it with minimal mixing.

This appears to be what the above linked Honda procedure tries to accomplish.


The goal is to thoroughly mix the old and new. That is the only way you remove more old fluid in subsequent drain/fills. Think of it this way. If you drained the pan and refilled with fresh ATF you now have about 3 qts of fresh ATF in the pan and about 7(I'm not sure what the total trans capacity is)quarts of old ATF in the rest of the system. If you then immediately do another drain/fill without running you car to mix old and new ATF, all you have done is replace the same 3 quarts you just added.



Oh I agree that you have to run it (not only that but have it shift). But WHY is the goal to throughly mix it?

It seems like the goal would be to get the 3 quarts new into the transmission and 3 quarts of old into the pan. (In most Honda Transmissions that would leave about 1-2 quarts old for the next process.

This seems to be what the above linked Honda procedure accomplishes.

 

[benjamming]

There is no pan.

 

[DuckRyder]

Originally Posted By: benjamming
There is no pan.


O.K. "Sump".

 

[artbuc]

I guess it all depends on how much backmixing occurs in the sump. Problem is that old ATF is returned to the sump at the same rate new ATF is being pumped into the system. If everything is completely mixed, you will drain about 70% old ATF at the next drain/fill. If you run the car for a short while, you may be removing ATF which is a lot less than 70% old.

 

[229]

It is a fluid circuit. I have explained how a fluid exchange machine works in a way a DIY person could do it without a $10K machine. You can let the transmission suck in the new fluid from a large container with the return hose. You can catch the old fluid from the other line in a recycling container. This produces the least waste from dilution. If it cannot be understood then let your mechanic do it.

 

[DuckRyder]

Originally Posted By: 229
If it cannot be understood then let your mechanic do it.


There is no need to be rude about it.

I understand your method perfectly.

 

[artbuc]

Originally Posted By: 229
It is a fluid circuit. I have explained how a fluid exchange machine works in a way a DIY person could do it without a $10K machine. You can let the transmission suck in the new fluid from a large container with the return hose. You can catch the old fluid from the other line in a recycling container. This produces the least waste from dilution. If it cannot be understood then let your mechanic do it.


This is what I didn't understand the first two times. Are you saying the return hose is also the suction (or supply) line to the pump? I guess you are because how else could the return hose "suck" new ATF from a large container? If this is true, how does ATF fill the sump? It would be very helpful if you would explain the path of the ATF flow. Apparently it is very different from a Toyota. In a Toyota, the return line just dumps into the sump which is at atmospheric pressure and the pump sucks ATF from the sump through a filter screen.

 

[229]

Originally Posted By: DuckRyder
Originally Posted By: 229
If it cannot be understood then let your mechanic do it.


There is no need to be rude about it.

I understand your method perfectly.


Was not directed toward you Robert.

 

[229]

Last attempt: Remove both ATF cooler lines. Crank engine noting which line has exiting fluid. Place that one, with an extention hose if needed, into a catch container. The other line will pull your new ATF into the tranny under it's own power. Around twelve quarts will exchange most light duty vehicles. HTHY

 

[DuckRyder]

Originally Posted By: 229
Originally Posted By: DuckRyder
Originally Posted By: 229
If it cannot be understood then let your mechanic do it.


There is no need to be rude about it.

I understand your method perfectly.


Was not directed toward you Robert.

In retrospect I see that, my apoligies!

 

[artbuc]

This is my last attempt too so we can end this once and for all. I FULLY understand what you are telling us to do. What I was asking for is a better understanding of this particular transmissions's hydraulic circuit because it is very different from anything I have owned. Specifically, how does the system design allow the gear pump to pull a vacuum on the cooler return line?

 

[229]

In case someone else takes offence, it was just a matter of fact statement. My son could not do it to save his life.

 

[229]

Originally Posted By: artbuc
This is my last attempt too so we can end this once and for all. I FULLY understand what you are telling us to do. What I was asking for is a better understanding of this particular transmissions's hydraulic circuit because it is very different from anything I have owned. Specifically, how does the system design allow the gear pump to pull a vacuum on the cooler return line?


It is best for a fluid circuit like this to keep a prime. On the Honda you could drain and refill the 3.5 quarts and then do what I described for transmissions in general. One advantage of this exchange method is not having to mechanically remove a pan and gasket. A disadvantage is not replacing the filter. Honda does not have an easily serviced filter. Even if you had a pan and changed the filter and refilled you could still do this method for a complete exchange. More transmissions are being put into service today without a dipstick and that maybe a difficult procedure to explain.

 

[229]

"Specifically, how does the system design allow the gear pump to pull a vacuum on the cooler return line?"

The cooler is just an area in the circuit used to cool the fluid. It already had to have a suction into the input of the pump to work in the first place and you are just opening the circuit. Do not only think of the pump side and forget the vacuum side or it will get confusing.
If you have used a sump pump to drain water then you know about the pull side and the push side. If the hose were connected around the pump then you would have a closed circuit. We have discussed opening the circuit and using each half for our benefit.

 

[artbuc]

Thanks. Yes, I always drain/fill first so the pump is sucking fresh ATF from the sump. On my Toyota, the pump pushes ATF through the cooler and back into the sump. I intercept the return flow - about 1 qt or so at a time. Then I shut off the engine and add back the same amount of fresh ATF. That way I never have to worry about the pump running dry. As I stated before, my Toyota can not pull fresh fluid into the system so I have to add it manually through the dipstick. The only way it could pull ATF into the system would be if I dropped the pan/filter and connected a supply directly to the pump suction line. This is how some machine flush systems work. I have never done this but it should work although it would be messy. You would have to have a good size receptacle to collect that portion of the flow that comes back through the valve bodies.

 

[229]

Next time safely let it idle in gear and see if it will pull the fluid in from a large container. You could also keep a constant flow going into the dipstick.